The forbidden “rough sex” defense has reared its head once more in the Soho House tub-strangle trial — this time in the deliberations room.

“There’s no evidence in this case regarding rough sex,” Manhattan Supreme Court Justice Bonnie Wittner told jurors this morning, warning them away from the dicey defense as the sensational trial entered its third day of deliberations.

Before going home last night, jurors had asked that testimony be read back today relating to “sex and rough sex” between accused strangler Nicholas Brooks, 27, and his alleged victim, beautiful swimsuit designer Sylvie Cachay, 33. Cachay, who designed for Tommy Hilfiger, Victorias Secret and her own brand, Syla, had been pulled dead from an overflowing bathtub at the exclusive hotel in December, 2010.

Brooks has been barred from claiming that rough sex prior to her death could explain away the fingerprint-sized bruises on Cachay’s neck, and her blood-shot eyes. Wittner has called the rough sex defense “speculative,” and prosecutors have termed it an offensive red herring.

Still, defense lawyer Jeffrey Hoffman has repeatedly tried to insinuate, in questioning throughout the month-long trial, that “rough sex” could provide an innocent explanation for the worst of the forensics.

Prosecutors have objected strenuously every time Hoffman has tread anywhere near the topic, including to bring up that DNA showed the couple had engaged in sex at some point, and that the large bruise at the very top of Cachay’s skull could have been consistent with her head being slammed into a headboard.

With the “rough sex” defense officially precluded, Brooks has had to pin his hopes on a “Whitney Houston” defense instead — claiming that the five prescription pain killers and anti-anxiety drugs found in Cachay’s system could have caused her to slip under the water, lose consciousness and drown accidentally.

Prosecution experts have shot that down, though — telling jurors that the drugs, prescribed for Cachay’s migraines and a pain condition called fibromyalgia, were all at therapeutic levels. There is no reason a “neurologically intact” person would accidentally drown in a bathtub, the prosecution has argued — and particularly not while wearing panties and a turtleneck sweater.

Since beginning deliberations on Tuesday afternoon, jurors have asked for virtually every piece of evidence in the month-long case, including autopsy and crime scene photographs, all evidence charts, and all of the text and email evidence.

Meanwhile, the prognosis from one alternate juror was bad for the defense.

“I would say it certainly looks bad for Mr. Brooks,” alternate juror number three, Charley Grant, 27, said after being released from the jury yesterday. “I mean, personally, I believe something happened in that room,” he said.

“There’s no reason for healthy young people to die like this,” he said, adding that he couldn’t be sure he’d convict, but that “I was close — I was close to saying they proved him guilty beyond a reasonable doubt.”